This invention relates to an integrator and an exposure apparatus employing an integrator.
In particular, this invention relates to an integrator devised for allowing hyperfine working to be performed in a photolithography process employed in manufacturing semiconductor devices and a reduction-projection excimer exposure apparatus using the integrator.
Conventionally, reduction-projection type exposure devices (steppers) which are commercially available use a superhigh voltage mercury-arc lamp as a source of light for the hyperfine working of semiconductor devices, especially, LSIs, VLSIs, etc. However, a conventional stepper uses a g-line (435 nm) and an i-line (365 nm) of a superhigh mercury-ark lamp, so that the resolution is 1.2 .mu.m for the g-line and 0.8 .mu.m for the i-line at most. It is virtually impossible to obtain a resolution of 0.5 .mu.m required for manufacturing 4-Mbit RAMs and 16-Mbit RAMs using those wavelengths.
Recently, the development of exposure devices which use an excimer laser source, for example, emitting Xecl (308 nm), KrF (249 nm) or ArF (193 nm) having a short wavelength compared to the g- and i-lines has begun to be studied.
Although the excimer light source provides high power, its illuminance in a plane varies in a range of not less than 10%. In addition, the beam diameter of the light source is small, for example, about 2 cm, so that it is necessary to change the beam shape to adjust to the mask and the reduction lens. In other words, it is necessary to expand the beam diameter with a uniform illuminance so that the entire mask is irradiated with light.